1. Field of the Invention
The present invention relates to a numerical control information generator for generating numerical control information for machine tools having a turret on the basis of overall machining shape and material shape input.
2. Description of the Related Arts
FIG. 8 is a block diagram showing an example of a conventional numerical control information generator. Procedures for generating numerical control information will now be described with reference to this block diagram.
In conventional equipment, a data inputting section 2 respectively stores the machining shape (part shape) PF and the material shape MF, which are input into a data inputting device 1 from outside, into a part shape storage section 3 and a material shape storage section 4. In addition, tool data DT comprising tool types, included angles, cutting edge angles, tool widths (grooving tools), diameters of holders, etc. is stored into a tool data storage section 5. A machining process deciding section 6 reads out the material shape MF and the part shape PF from the respective storage sections 4 and 3, and extracts the whole cutting zone to be machined from the difference between the material shape MF and the part shape PF. In addition, the machining process deciding section 6 reads out the tool data DT, and divides the extracted whole cutting zone into sub-cutting zones which can be machined using the respective selected tools. That is to say, the machining process deciding section 6 decides the machining processes MP necessary for machining the part shape PF by estimating the sub-cutting zones which can completely remove the whole cutting zone of the part shape PF.
Next, a cutting condition deciding section 7 successively reads out the decided machining process MP, and decides the machining conditions MC for the respective machining processes MP. The decided cutting conditions MC are stored into a process data storage section 8. A machining order deciding section 9 successively reads out the machining processes MP stored in the process data storage section 8, and stores them again into the process data storage section 8 after rearranging them as an appropriate machining order MN. A numerical control information generating section 10 generates numerical control information NC by reading-out the material shape MF stored in the material shape storage section 4 and a process data DM such as the machining process MP, the cutting conditions MC, the machining order MN, etc., which are stored in the process data storage section 8. The numerical control information NC is output to the outside via a numerical control information outputting section 11 as a form of media 12 such as a communication circuit, a magnetic disk, or paper tape.
Processing for deciding the machining process MP in the conventional numerical control information generator will now be described in detail.
The number of tools mountable on a turret (tool post) of a lathe depends on the structure of the turret. For example, it could be eight or twelve. Let us consider the case of machining using a lathe which can simultaneously mount eight tools as an example. The automatic generation of machining processes performed by the prior art for the shape shown in FIG. 9 (bar materials, threads and grooves on external and internal surfaces) will be described with reference to the flow chart shown in FIG. 10.
When an operator registers a mountable number (8) of tools with this equipment (S1), the part shape PF and the material shape MF, which are already input, are read out (S2). The whole cutting zone to be machined is extracted by taking the difference between the two shapes (S3). Next, let us assume that a drill has been selected as the result of the search of the tool data in order to machine the bore (S4). The zone to be machined by the drill is estimated from the tool shape such as the diameter and the point angle of the drill, and the drilling processes and the drilling conditions are decided (S5, S6). Next, the process for removing a part which is uncut by the drill tip is decided as end milling. In addition, a tool for the bore (boring bar) is selected, and the remaining roughing and finishing processes are decided. Thus, when a plurality of tools are used for one cutting zone (machining position), a plurality of machining processes are decided. That is to say, machining processes are decided by machining positions and tools to be used. Such procedures are repeated for the whole processes (S4-S7). In the case of FIG. 9, for example, eleven machining processes in total such as 1. drilling, 2. rough end milling, 3. rough outer face cutting, . . . 11. internal threading cutting are decided.
If the number of tools necessary for the machining is less than the number of simultaneously mountable tools (S8), the numerical control information is generated after deciding the overall machining order by rearranging the respective machining processes decided separately (S10, S11). If it is checked whether or not the required machining can be accurately carried out (S12), simulation of the machining can be conducted by interpreting the generated numerical control information (S13, S14).
On the other hand, if the number of the tools necessary for machining exceeds the number of the simultaneously mountable tools in step 8, it is impossible to machine the workpiece using the tools mounted on the turret. For example, if all of the tools are different for all of the machining processes, eleven tools are necessary for the part shape shown in FIG. 9. Therefore, this shape can not be machined using the simultaneously mountable 8 tools. When more tools than the number of simultaneously mountable tools are necessary like this, the processing ends showing an error message such as "Number of tools is over the limit", during the automatic generation (S9).
As mentioned above, in the conventional numerical control information generator, when more tools than the number of simultaneously mountable tools are necessary, an operator should perform a process editing operation, such as separation of external/internal thread cutting, using an additionally provided editing means, not shown in the figure, so as to perform the machining using less tools than the number of simultaneously mountable tools.
In addition, when the machining is intended to be carried out by separating it into the internal part and the external part beforehand, manual operations from the shape input to the preparation of the machining programs become necessary for two machining shapes of the internal part and the external part respectively. Therefore, there is such a problem that this method requires a lot of time and labor for an operator.